Published: Jan. 30, 2019

Authors: Raul A. Monsalve, Anastasia Fialkov, Judd D. Bowman, Alan E. E. Rogers, Thomas J. Mozdzen, Aviad Cohen, Rennan Barkana, Nivedita Mahesh

Abstract: We present new constraints on parameters of cosmic dawn and the epoch of reionization derived from the EDGES High-Band spectrum (90−190 MHz). The parameters are probed by evaluating global 21 cm signals generated with the recently developed Global21cm tool. This tool uses neural networks trained and tested on ∼30,000 spectra produced with semi-numerical simulations that assume the standard thermal evolution of the cosmic microwave background and the intergalactic medium. From our analysis, we constrain at 68% (1) the minimum virial circular velocity of star-forming halos to Vc<19.3 km s−1, (2) the X-ray heating efficiency of early sources to fX>0.0042, and (3) the low-energy cutoff of the X-ray spectral energy distribution to νmin<2.3 keV. We also constrain the star-formation efficiency (f∗), the electron scattering optical depth (τe), and the mean-free path of ionizing photons (Rmfp). We re-compute the constraints after incorporating into the analysis four estimates for the neutral hydrogen fraction from high-z quasars and galaxies, and a prior on τe from Planck 2018. The largest impact of the external observations is on the parameters that most directly characterize reionization. Specifically, we derive the combined 68% constraints τe<0.063 and Rmfp>27.5 Mpc. The external observations also have a significant effect on Vc due to its degeneracy with τe, while the constraints on f∗, fX, and νmin, remain primarily determined by EDGES. Read more via arXiv or via The Astrophysical Journal.